Gas streams often carry particulate material therein. In many instances, removal of some or all of the particulate material from a gas flow stream is essential. For example, air intake streams to engines for motorized vehicles or power generation equipment, gas streams directed to gas turbines, and air streams to various combustion furnaces, often include particulate material. The particulate material can cause substantial damage to operating equipment. The particulate is preferably removed from the gas flow upstream of the engine, turbine, furnace or other equipment.
In other instances, production gases or off gases may contain particulate material, for example, those generated by processes that included milling, chemical processing, sintering, painting, etc. Before such gases can be, or should be, directed through various downstream equipment and/or to the atmosphere, a substantial removal of particulate material from those streams is important.
The invention relates to filter elements in structures and to improved filter technology. The invention also relates to polymeric compositions with improved properties that can be used in a variety of related applications including the formation of fibers, microfibers, nanofibers, fiber webs, fibrous mats, permeable structures such as membranes, coatings or films. The polymeric materials of the invention are compositions that have physical properties that permit the polymeric material, in a variety of physical shapes or forms, to have resistance to the degradative effects of humidity, heat, air flow, chemicals and mechanical stress or impact in filtration structures and methods.
In making non-woven fine fiber filter media, a variety of materials have been used including fiberglass, metal, ceramics and a wide range of polymeric compositions. A variety of techniques have been used for the manufacture of small diameter micro- and nanofibers. One method involves passing the material through a fine capillary or opening either as a melted material or in a solution that is subsequently evaporated. Fibers can also be formed by using “spinnerets” typical for the manufacture of synthetic fiber such as nylon. Electrostatic spinning is also known. Such techniques involve the use of a hypodermic needle, nozzle, capillary or movable emitter. These structures provide liquid solutions of the polymer that are then attracted to a collection zone by a high voltage electrostatic field. As the materials are pulled from the emitter and accelerate through the electrostatic zone, the fiber becomes very thin and can be formed in a fiber structure by solvent evaporation.
As more demanding applications are envisioned for filtration media, significantly improved materials are required to withstand the rigors of high temperature 100° F. to 250° F. and up to 300° F., high humidity 10% to 90% up to 100% RH, high flow rates of both gas and liquid, and filtering micron and submicron particulates (ranging from about 0.01 to over 10 microns) and removing both abrasive and non-abrasive and reactive and non-reactive particulate from the fluid stream.
Accordingly, a substantial need exists for polymeric materials, micro- and nanofiber materials and filter structures that provide improved properties for filtering streams with higher temperatures, higher humidities, high flow rates and said micron and submicron particulate materials.